Trade education and workforce development are two initiatives we value highly here at Dunn Lumber, so it should come as no surprise that we have close ties with Seattle Central College's Wood Technology Center (WTC). With roots dating back to the early 1900s, WTC's history intersects with ours at Dunn Lumber at various points (our very own Ed Dunn Jr. took some classes at Edison), and we're proud to be connected with such an exemplary educational institution.

Throughout the episodes in this series, we'll be speaking with Dave Borgatti, a long-time faculty member at the WTC, about the center's history, program offering, and various topics in woodworking education. Dave got his start in woodworking as a boat builder in Portland, Oregon, for Schooner Creek Boat Works, and ended up at WTC as an instructor in 1992. Since then, Dave has helped countless students—from boat builders to carpenters and cabinetmakers—learn the woodworking craft.

We’re back with part two of our Biscuit Joiner 101 discussion. In the first part (watch it here), we went over what a biscuit joiner does and why it’s useful in a variety of projects. Today, Dave demonstrates how to actually use a biscuit joiner to make sturdy, seamless joints. Watch our discussion in the video above, or keep reading for a detailed recap. 

How to use a biscuit joiner

Biscuit joiners are pretty easy tools to use. As with any power tool, make sure you have your protective gear on, including eye and ear protection, before beginning work.

1. Make test cuts

Start by making a test cut, or “plunge,” into a piece of scrap wood that is the same thickness as your workpiece. This way, you can check that the slot, or "kerf," is at the depth you want and centered in the material thickness. 

First make a cut with the biscuit joiner set on the #20 depth of cut. Insert the biscuit and draw a pencil line across the biscuit. Rotate the biscuit 180º and reinsert it into the kerf. If the line disappears, the machine is set up properly. If the line still shows, use the turret on the side of the joiner to adjust the depth slightly deeper.

To center the plunge in your wood, adjust the joiner fence up or down to center the kerf in the material. It doesn’t need to be exact, but you want to biscuit your wood as close to the center as possible. 

After making adjustments, do another test cut. If the cut looks centered, you’re ready to move on to using the biscuit joiner on whatever pieces of wood you want to join together.

2. Mark joint

Arrange the two pieces of wood you are connecting where they should be joined, and then mark joint. Only mark across the joint—not across the full material thickness or width. Otherwise, you won’t be able to tell which face is which when you are cutting and assembling the wood. (Watch the video at 3:07 to see what we mean.)

Biscuit joiner diagram
3. Make cuts

Now it’s time to make your cuts. For some pieces of wood, you can simply lay them down flat on your work surface and steady them with one hand as you use the biscuit joiner with the other. For pieces that need to be vertical when you make your cut, set up stop blocks and then clamp your wood to the blocks. This holds them securely in place.

4. Insert biscuit and connect

When you are ready to assemble the joint, apply adhesive to both kerfs and insert a biscuit. Remember that when you are working with waterborne adhesives, you have only 3-4 minutes to make this assembly, otherwise the biscuit will swell and not fit in the kerf. Tightly clamp the workpieces until the glue sets.

How to use a biscuit joiner for miter cuts

While biscuit joiners are often used for joining wood at right angles, some joiners have fences that can be tilted to match a miter. To do this, unlock the tool's fence and tilt it to bear flat on the end of the stock. Keep in mind that doing this will change the center of the joint, so be sure and adjust the fence upwards and center the kerf in the material.

Safety tips for using biscuit joiners

Generally speaking, a biscuit joiner is a pretty safe tool. Since it’s spring-loaded, the blade retracts into the machine and is only out when it’s plunging into a piece of wood. It also has a trigger lock, which allows you to leave the machine on with no issue.   

That said, it’s always smart—and safer—to use stop blocks (as mentioned above) to help hold your wood in place without risking placing your fingers in spots where you could potentially nick them with the machine.  

It’s important to recognize that a biscuit joiner is not a very ergonomic tool and can wear out your wrist. To ensure correct cuts, maintain safety, and protect your wrist, it’s smart to go slow.

For more woodworking tips, tool explanations, and tutorials, check out other episodes from our Wood Technology Series. In this series, we cover everything from the history of lumber sizing and naming to the difference between planers and jointers, and so much more.